Joosten, who won two Emmys for her portrayal of Mrs. McCluskey on Housewives, passed away in Westlake Village, Calif. She had first battled lung cancer back in 2001, but survived. She was diagnosed with the disease a second time in 2009, but after undergoing surgery and chemotherapy, she was declared cancer-free again in 2010. In recent years, she was an advocate for lung cancer awareness and research. Her guest-star turns on My Name is Earl and Grey's Anatomy centered on her character's attempts to quit smoking.

Joosten first rose to fame in 1999 for playing Mrs. Landingham, President Bartlet's secretary on The West Wing. She recurred on the NBC drama for two seasons until her character was killed in a car crash in 2001. She went on to appear in more series, including The X-Files,Will & Grace, Gilmore Girls, Scrubs and even played one incarnation of God on several episodes of Joan of Arcadia.

In 2004, Joosten won her most notable role, as Karen McCluskey on Desperate Housewives. She won the Emmy for outstanding guest actress in a comedy series twice, in 2005 and 2008, and was promoted to a series regular in Season 6. After her character's tragic end on The West Wing, Joosten famously made Housewives creator Marc Cherry promise not to kill her off the show. In a bittersweet moment, the ABC soap's series finale was largely built around her character's death from terminal lung cancer — to the tune of Johnny Mathis' "Wonderful! Wonderful!"

"The character of Mrs. McCluskey was created for a single episode," Cherry said in a statement obtained by EW. "We then cast Kathryn Joosten and she infused the part with so much feisty wit and curmudgeonly bravado, we knew we had to move her onto Wisteria Lane for the run of the series. I will forever miss her, as a co-worker and as a friend."

Felicity Huffman, who shared the most screen time with Joosten throughout Desperate Housewives' eight-year run, tweeted about her late co-star Saturday. "All my prayers and love to Kathryn Joosten's family. Rest in peace. She was an amazing woman and a wonderful actress."

Another ex-Wisteria Lane resident, Marcia Cross, echoed Huffman's sentiments on Twitter. "Thank you Kathryn. For your courage, your humor, your fight and your talent. We were so lucky to have you."

West Wing alum Rob Lowe paid his final respects to Joosten and also gave a shout-out to their late co-star, John Spencer, who played Leo McGarry on the drama. Spencer died of a heart attack during the show's final season, and his character also died of a heart attack during one of the last episodes. "Goodbye Kathryn; our beloved Mrs Landingham. You will never truly be gone, film is forever. Tell Leo I love him."